Nanotechnology for Improved Three-Dimensional Concrete Printing Constructability

This paper investigates the application of nanotechnology in three-dimensional (3D) concrete printing (3DCP), in particular for enhancing thixotropic material behavior, improving buildability or the vertical building rate, and the amelioration of typical 3DCP anisotropic mechanical properties. Two 3D-printable cementitious materials are investigated in this study: 1) high-performance concrete (HPC) with respective nano-silica (nS) and silicon carbide (SiC) nanoparticle additions; and 2) lightweight foamed concrete (LWFC) with nS addition. The results indicate a significant increase in thixotropic material behavior for the HPC at low nanoparticle dosages. The inclusion of SiC nanoparticles improved the HPC's buildability performance by 45%. The incorporation of 3% nS to the LWFC increased the static yield shear stress by up to five times, which is validated by the improved buildability performance. Hardened state mechanical properties improved for both cementitious materials and nanoparticle additions. Especially noteworthy is nanoparticles' favorable influence on the interlayer bond strength. Keywords: buildability; high-performance concrete (HPC); interlayer bond strength; lightweight foamed concrete (LWFC); mechanical properties; nanoparticles; rheology; thixotropy; three-dimensional (3D) concrete printing.